When backfilled soil causes strain, bulges in basement walls can result.
Perhaps the most catastrophic failures that we’ve witnessed in our inspection careers have been fully-inward-bulged (collapsed) basement foundation walls. Each failed wall (made entirely of hollow core concrete block) literally exploded into the basement followed by a river of mud or earthen landslide. If anyone had been sitting or standing near the wall at the time of failure, we doubt they would have survived. Fortunately, we’ve never heard of a serious injury or lost life, but we have witnessed the emotional grief/anguish that ensues once the homeowner finds out that their insurance policy will not cover the cost of cleanup or repair. Obviously, these costs can easily exceed tens of thousands of dollars.